Foamed seal package



Sept. 12, 1967 "r. o. CURRAN I I FoAMEp SEAL PACKAGE Filed June 1, 1965INVENTOR. THOMAS D. CURFPAN ATTORNEYS United States Patentv O 3,341,105FOAMED SEAL PACKAGE Thomas D. Curran, Walnut Creek, Calif., assignor toFibreboard Paper Products Corporation, San Francisco, Calif., acorporation of Delaware Filed June 1, 1965, Ser. No. 460,250 3 Claims.(Cl. 229-37) The present invention relates to methods for sealingpackages, and more specifically to a method of sealing packages whereinan expandable material is utilized to fill all gaps and voids in thepackage closures.

Paper, paperboard and plastic film containers, which are utilized toform packages for particular goods such as food, cleaning materials andother perishable products, must fulfill a number of functions. Amongthese functions the package must protect the contents, depending upontheir nature, from moisture change; deterioration in texture, flavor andgeneral market acceptability due to oxidation and light; sifting, wherethe product is powdered or granular, through package gaps or openings;and the entry of insects or other foreign material such as dust, dirt,etc.

In order to protect the contents from the above noted types ofdeterioration, the industry has resorted to heatsealed bags, pouches andoverwraps or inner containers of thin papers coated with wax or plasticor other polymeric film materials. Such wax papers or plastic filmsprovide barrier protection and generally produce good, acceptable, tightclosures. Such thin barrier materials have several disadvantages,however. For instance they do not alone provide the necessary structuralstrength required for many fragile products such as cereals. Unlessupported by other means, these thin materials do not stack well orprovide a sufiiciently flat surface for good display of advertisingmessages. Further such thin film packages are subject to breakage,especially in larger unit packs. Additionally, packaging line speeds aregenerally much lower for pouches and overwraps than for rigid orsemirigid carton materials. These lower packaging line speeds generallyincrease the over-all cost of using such thin film materials.

In view of the limitation of such thin film materials as pointed outabove, many packages not only use these thin film barriers, but alsoincorporate a rigid or semirigid paper or paperboard carton therewith.For instance many dried fruits are packed with an inner sealed bag ofWaxed paper or plastic film, a folding paperboard carton container, plusa printed wax paper or plastic film overwrap. Many cereals are packed indouble or single barrier bags with a printed folding carton, while stillothers are packed in a plain carton with a printed barrier overwrap.Frozen foods almost from their introduction into home use have usedunprinted wax paperboard cartons with a printed heat sealed wax paperoverwrap.

While such multiple containers as noted above generally do an excellentjob of protecting the products packaged therein, it can also beunderstood that such packages not only require an excessive amount ofmaterials of difierent varieties to produce the package but furtherinvolve repetitive packaging operations which greatly tend to increasethe price of the product. In addition the multiple'operations necessaryto package the product result in greater total packaging line times withsubsequent in- "crease in ultimate cost.

For the above reasons the industry has made a concentrated developmenteffort on packages which combine the structural strength of a semi-rigidor rigid paperboard carton combined with the barrier properties of waxpaper or plastic film bags and overwraps all in one structure. Suchcontainers as have been developed are known as wrapperless cartons orsingle wall structure cartons. Such wrapperless cartons offer theadvantages of reducing the variety of materials necessary to package theproduct, eliminating many operations in the packaging process, thusreducing labor requirements with consequent cost reductions, permittinghigher machine speeds on packaging lines through the use of rigid orsemi-rigid materials only, the utilization of special conveniencefeatures such as easy-opening tear strips and recloseable spouts forpour-and-store items, and increased protection of the package integritysince the necessary barrier films are strongly adhered to the more rigidpaperboard. The consequence of which is that such wrapperless packagesare not as subject to damage and loss of barrier protection in handlingas previous multi-layer packages.

Although presently available wrapperless containers offer many of theadvantages indicated above, they are still subject to the problems ofany single barrier package, in that the closure areas are particularlysusceptible to the formation of gaps and openings (especially at thecorners) wherein the primary problems of sifting, insect and foreignmatter entry, and oxidation are still present. Further steps to combatthese problems have also been taken through the introduction of extrasealing flaps, addition of thin membrane films glued to the closureportion of the container, and sealing of the sealed package by dippingin melts of wax or other plastics. However, all such processes involvethe addition of extra materials to the package or extra operations whichonce again tend to increase the packaging costs and packaging time. Thusthe closing of corner holes and flap gaps has been found to be the majorproblem remaining in the wrapperless package.

The present invention presents a method of sealing packages wherein gapsand other holes in the closure portion, including the corner holes of apackage, are effectively and securely eliminated without theintroduction of additional materials, extra closure flaps or otherspecial design, and without the introduction of additional steps intothe packaging operation. Briefly the method of the present inventioninvolves the use of a material that expands or foams" to fill all gapsand hole in the package closure.

Is is, therefore, an object of the present invention to provide a methodof sealing packages wherein a foamed material fills all gaps and holesin the package closure.

It is another object of the present invention to provide 'a' method ofsealing packages wherein extra flaps or special designs of the cartonare eliminated from the closure.

It is another object of the present invention to provide a method ofsealing packages wherein the container glue or adhesive not only sealsthe package flaps, but also expands or foams to fill all gaps or voidsin the pack age.

It is yet another object of the present invention to provide a method ofsealing packages wherein the package is sealed with an expandingadhesive which not only glues the package flaps, but also expands tofill all gaps or voids in the package closure wherein sifting, easyinsect or foreign matter entry, and oxidizing gas entry, is eliminated.

The invention will be better understood from the fol lowing descriptiontaken in conjunction with the accompanying drawing of which:

FIG. 1 is an isometric view of one end of a typical wrapperless cartonshowing the end flaps in the opened position but with the sealingmaterial applied thereto just prior to the sealing operation;

FIG. 2 is an isometric view of a closure portion of the typical packageof FIG. 1 illustrating the package after the end flaps have been closedand the gaps and holes have been filled by the foamed material; and

FIG. 3 is a cross-sectional view of the package of FIG. 1 across the endclosure thereof.

In the practice of the present invention any wrapperless paperboardcarton of simple conventional design may be utilized. The end flapclosure construction of the carton may be extremely simple, like thatconstruction as illustrated in FIGS. 1 and 2 of the drawing.

While the drawing illustrates a simple noncomplicated carton, it shouldbe understood that other carton designs, even of a more complex nature,may be utilized equally well in the practice of the present method.

Specifically, with reference to FIG. 1, a carton 11 is formed with sidewalls 12, 12, 12" (and another one which is not shown) to form agenerally rectangular inner volume. One of the side walls 12 is extendedto form an end flap 13, while each of the other sides is similarlyextended to form end flaps 14 and 16 and a fourth end flap not shown inthe illustration. A fold line 17 defines the junction between side wall12 and end flap 13, while fold lines 18 and 19 define the junctionbetween side wall 12' and end flap 14 and side wall 12" and end flap 16,respectively. A similar fold line is formed between the fourth side Walland fourth end flap not shown in the illustration. End flap 13 is cut toa length whereby the upper edge 21 thereof will extend approximatelypartially across the end opening of the box when the flap is folded atright angles to side wall 12. End flap 14, on the other hand, is cut toa length slightly shorter than the length of fold line 17 whereby itsupper edge 22 will nearly touch, or at least come in close proximity, tothe opposite wall of the carton when flap 14 is folded at right anglesto side wall 12. Similarly end flap 16 is cut to a length approximatelyequal to the length of fold line 17 whereby its upper edge 23 willextend all the way across end flap 14 when folded down at right anglesto side wall 12". The fourth flap (not shown) is cut to a length equalto that of end fiap 13 whereby when it is folded down it will extendinwardly of its respective side wall.

FIG. 1 illustrates the carton 11 at a time just prior to the folding andsealing operation during the practice of the method of the invention, sothe material that serves to glue the end flaps of carton 11 together ishown applied to the flaps. Thus a patch of material 24 is shown appliedto the upper surface of flap 13 adjacent its upper edge 21, anotherpatch of material 26 is shown applied to the upper surface of flap 14adjacent its upper edge 22, and another patch of material 27 is shownapplied to the under surface of flap 16 adjacent its upper edge 23.Another patch of material similar to that of patch 24 is applied to thefourth flap (not shown).

It should also be noted that small patches of material 28 and 29 areapplied to the upper surface of flap 13 adjacent the end of fold line 17thereof. Similar patches are applied to the identical position of thefourth flap which is not shown in the illustration.

It will be apparent that the extent and positioning of the patches maybe varied depending upon the end flap shapes and folding procedures. Ofcourse the patches can be placed in other positions at any portion ofthe carton body, if it is intended to seal any gaps or channels. Howeverit is only necessary to apply the material in such cations as to ensuresecure sealing of adjacent flaps when the carton is folded and furtherin such amounts as to force the expanding material into all gaps andhole areas of the closure. The carton construction of the drawing ismerely one of a great number of closure configurations in use andvariations in placement of material and amounts used for each type ofcarton construction and size variation will be apparent to those in thepackaging industry.

The material utilized to form patches 24, 26, 27, 28, 29 and otherpatches on the end flaps of the carton is critical to the operation ofthe present invention. Specifically, the material must be composed of amaterial having the following properties: (I) It must be capable ofadhering to the two adjacent surfaces of paperboard or other cartonmaterial. (2) It must have the property of expanding and flowing afterapplication to the carton surface and prior to setting.

Many self-foaming plastics are suitable materials for use as thematerial in the present invention. Specifically, the material utilizedto seal any gaps or channels in the carton 11 may be any suitablematerial that foams up or expands under the proper conditions. It isonly necessary that such material adheres to the adjacent carton wallsand that the resultant foamed structure be stable under any expectedenvironmental conditions to which the package is subjected.

For instance it has been found that polyethylene can be foamed usingp,p'-oxybisbenzenesulfonylhydrazide as a blowing agent. In this instancethe blowing agent, in powder form, is melted into the polyethylene belowits decomposition point. The plastic polyethylene-blowing agent melt isthen applied to the carton 11 in thin films in the positions referredto. The opened flaps are heated by a hot air blast at a temperaturebetween 400-1000 F. for a period of 1-10O seconds, depending on thespeed of the machine. The flaps are closed and kept under heat andpressure until the polyethylene has expanded into the gaps and channelsin carton 11. On cooling the polyethylene solidifies, thus keeping thecarton tightly sealed.

The foamable polyethylene can either be applied in a patterned form asshown or additionally in areas where glue would normally be applied, inwhich case it may function as a sealant at critical edges and corners,but also act as an adhesive for securing the end flaps in place.

Usually foamable polyethylene can best be used on a heat sealable coatedsurface, where the majority of the adhesion of the end flaps to oneanother would be accomplished by the heat seal coating, while thepatterned foamed polyethylene would protect the critical areas havingholes and channels.

While such a foamable material is suitable for use in the invention,other materials are also particularly well suited for use therein andespecially preferred. Thus, polyether foam systems such as polyurethaneare especially desirable. This is particularly so, since polyurethanenot only forms an excellent foamed material for sealing gaps andchannels, but in addition, strongly adheres to the usual cartonmaterials. Thus the polyurethane serves the dual purpose of foaming toseal carton gaps and channels and gluing the carton together. Utilizingsuch a material eliminates the need for separate adhesives or heatsealable surface coating to effect carton sealing. However, it should beunderstood that under certain circumstances, separate adhesives andfoaming materials are the desirable materials for effecting cartonclosure and gap sealing.

With respect to the single adhesive-foam systems, polyether systems suchas are used in the preparation of rigid unicellular polyurethane foamhaving density from about 2 to 30 or more pounds per cubic foot, havebeen found to be particularly suitable for use in the present invention.

Such polyether foam systems are well known in the industry and arecommercially available from several sources. For instance one suchsystem known as Polyite is available from Reichold Chemicals Inc. Thissystem basically employs two separate products, a resin and aprepolymer. The resin component contains a catalyst and a suitableblowing agent, usually a fluorocarbon. The prepolymer comprises aselected isocyanate, which when contacted with the resin component,reacts to polymerize to a self-foaming, self-curing unicellular materialhaving the desired adhesive and expansion properties.

The product foamed adhesive is produced by properly mixing in thecorrect ratio the required amounts of the system components. Mixing canbe carried out either batchwise or with automatic metering, mixing anddispersing equipment.

In any event, the mixture, if a single adhesive-foam, or the separateadhesive and foam material, if a two component system, is applied in athin film to the proper areas of the package end flaps as pointed outabove. The end flaps are then immediately folded over and held underpressure until the foam cures sufliciently and forms a bond to theadjacent surfaces of contact of the carton. Machinery for automaticallyfolding and holding the cartons until the bond forms is common in theindustry and is readily available for this purpose.

FIG. 2 illustrates the carton of FIG. 1 after end flap 13 and itsopposite flap (not shown) have been folded in, end flap 14 has beenfolded over the inner flap and outermost flap 16 has been folded overthe entire end of the carton.

The end flaps 13, 14, 16 and flaps 13 opposite flap are foldedimmediately after application of the adhesive or foam material patchesthereto. The flaps are held in the folded position while the materialcures during which time it foams and expands into adjacent areas. Thusthe end gap 31 created where the edge 22 of flap 14 overlies theunderneath flaps, and where the under surface of end flap 16 is foldedthereover, is filled by the material expanding thereinto.

Similarly any holes or gaps occurring at corners 32 and 33 of the cartonare filled by patches 28, 29 expanding thereinto. Similarly all othergaps and holes occurring in the end closure of the carton are filled bythe expanding material.

As the material expands into the gaps and holes in the carton structureit solidifies into an impermeable foam structure. Also, in the event asingle adhesive-foam system is used, the material forms an excellentadhesive, it securely adheres to adjacent portions of the cartonstructure to provide a secure seal of the gap or holes, as well as theend flaps, during subsequent handling operations.

After the material has solidified any flashing material that is extrudedfrom the edge of the flaps or out through the holes and gaps may beremoved by a simple abrasive or cutting operation. In fact, oncesuflicient experience is had with a particular carton design and size,exact amounts of expandable material may be applied thereto whereby anyexcess amount is eliminated and such subsequent abrasive or cuttingoperation to remove flashing is eliminated.

Semi-rigid or flexible closed cell foam materials, as well as rigid foammaterials, are suitable for use as the expandable material in practicingthe method of the invention. The selection of a semi-rigid or flexibleclosed cell foam for use as the gap filling material of the package willdepend upon the use to which the package is to be put and the conditionsexpected during its transportation and storage. For example, wherepackages may fall on a corner, a flexible foam which is not so subjectto break-age as a rigid foam would be a suitable material for fillingthe corner holes of such packages.

Experiments were conducted to compare cartons sealed by the method ofthe present invention with other cartons of identical design sealed byother prior art means. Table I below presents data obtained on alock-style carton made out of paperboard having a 1 mil polyethylenecoating on the outside and a web wax coating on the inside thereof.

One of these cartons, prepared by the method of the present invention,had the flap areas thereof coated with a freshly prepared polyurethanefoam mixture of about 2 /2 pounds per cubic foot density. The flap areaswere then locked in position and held under a pressure of a few poundsper square inch weight. After a few minutes the bond was suflicientlystrong to allow removal of the pressure. This carton, along with othercartons produced by other methods known in the art, was then tested in adiffusion apparatus which measured the percentage of moisturetransmission through the carton structure. The results of thesetests-are illustrated in Table I.

TABLE I Moisture vapor transmission Specimen rate at 100 F., 88%relative Percentage humidity difference, grams transmission per 100 sq.ins. per day (1) Total carton moisture vapor trans. rate 22. 5 100 (2)Carton w/one locked end sealed with mierowax 8. 14 35. 9 (3) Cartonw/both locked ends sealed with mierowax 3. 86 17. 9 (4) Carton w/bothlocked ends and easy opening perforations sealed with microwax 2. 83 12.4 .(5) Carton sealed by method of the 6. 4

invention 1.

Table I above illustrates that a carton laboratory sealed by the processof the present invention is more tightly sealed than a similar carton inwhich all vulnerable leakage points were laboratory sealed withlocalized applications of hot microwax. The results of the tests inTable I were made utilizing apparatus and testing methods fullydisclosed and described in an article entitled, Test Sealed CartonBarriers Quickly and Reliably, by T. David Curran and Gordon C. Wheeler,appearing in volume 10, No. 2, February 1965 edition of the publicationPackage Engineering.

The results of another series of tests utilizing apparatus comprisingtwo matched fiowmeters is presented in Table II. The outlet of oneflowmeter was sealed into the package interior, while the input to thesecond flowmeter Was also sealed into the package interior. A small airpump and ancillary equipment gave a smooth regulated flow of air. Theair flow rate was controlled by a needle valve. If a package had noleakage both input and output flowmeters would read the same. If leakageoccurs the output flowmeter reading falls off directly in proportion tothe loss through the package walls.

Such tests, that determined air leakage rates from the various packagessealed as indicated in the table, are a measure of the absolute sealachieved by the different methods. It will be noted that test (5) showspackages sealed according to the method of the present invention. Afurther review of such results will reveal that such methods producedpackages far better than any other method with the exception of triplebarrier packages comprising successive layers of heat sealedpolyethylene, foil and a paper pouch. This improvement may be understoodby remembering that conventional water based adhesives used in gluingpackages shrink considerably on drying to about 10 to 30% of theirvolume when applied wet. Hot melt adhesives remain about the same volumeor shrink slightly on solidifying, however, the foamed adhesive used inthis invention can be made to expand as much as fifty-fold its initialvolume at application, and in addition it remains flowable long enoughto allow gaps and holes to be completely filled.

TABLE II.AIR LEAKAGE RATES OF COMMERCIALLY SEALED PACK- AGES VS. FOAMSEAL GARTON AT 4.34 LITRES/MIN. INPUT FLOW Package Package leakage,leakage rate, Package description Product packaged litres/min,litres/min,

individual avg.

values (1) Glue end carton, paper/poly- Sugar 4.34; 3.78; 2.77 3. 6

ethylene/paperboard sandwich w/ metal pour spout.

(2) Cellopane wrap, heat sealed Raisins 2.54; 2.73; 2.33 2. 5

over carton.

(3) Reyseal foiloverwrapped carton, Water condi- 1.94; 1.42; 2.85 2. 1

papcr/microwax/i'oil lamination tioner. heat sealed.

(4) tEll/axed paper overwrapped Raisins 4.34; 3.99; 1.94 3.4

car on.

(5) Paperboard carton w/polyethyl- 0.14; 0.44; 0.39 0.3

ene coating, both sides sealed w/ olyurethane foam.

(oi laperboard carton w/V an Buren Powdered deter- 1.93; 2.54; 2.44 2. 3

ears. gen

(7) Paperboard carton overwrapped Corn Starch 1.14; 3.08; 2.35 2. 2

w/glued paper.

(8) Heat sealed polyethylene/foil/ Dehydrated .0; 0.19; 0.09 0.0.9

paper pouch. potato granules.

(9) Heat sealed polyethylene bag Dehydrated 0.82; 0.19; 1.14 0.7

potato flakes.

Considering the purposes and eifects of the method of the invention willalso reveal that not only may gaps and channels be sealed in packagesbut, in addition, other useful results can be achieved. For instance, itis oftentimes desirable to exclude moisture vapor, gas and liquid watertransfer through the interior channels of corrugated paperboard panelsor boxes. Utilizing the method of the invention a film of expandablematerial is applied to the open ends of such paperboard. Subsequently,the material is permitted to cure, whereby it foams, expands, and flowsinto the open channel ends; or if a heat sensitive foaming material isutilized, hot air is blown on the coated ends of the paperboard, wherebythe material foams, expands and fills the ends of the channels in thepaperboard. Thus the corrugated paperboard has its open ends sealed bythe expandable materials, and moisture vapor, gas and liquid watertransfer through the interior channels thereof is eliminated.

Other applications and uses of the method of the present invention willbe apparent and all such are contemplated by this specification asparticularly encompassed by the following claims.

What is claimed is:

1. A wrapperless package including a closure portion having overlappedclosure flaps with holes, gaps and channels therebetween, said flapsbeing adhesively sealed by an adhesive composition comprising a closedcell foam structure which fills said holes, gaps and channels.

2. The wrapperless package of claim 1 wherein the closed cell structureis formed of blown polyethylene.

3. The wrapperless package of claim 1 wherein the closed cell structureis formed of polyurethane.

References Cited 45 JOSEPH R. LECLAIR, Primary Examiner.

DAVIS T. MOORHEAD, Examiner.

1. A WRAPPERLESS PACKAGE INCLUDING A CLOSURE PORTION HAVING OVERLAPPEDCLOSURE FLAPS WITH HOLES, GAPS AND CHANNELS THEREBETWEEN, SAID FLAPSBEING ADHESIVELY SEALED BY AN ADHESIVE COMPOSITION COMPRISING A CLOSEDCELL FOAM STRUCTURE WHICH FILLS SAID HOLES, GASP AND CHANNELS.